The purpose of the invention is to make possible the monitoring of a chemical reaction with a very simple low cost device. The device not only has the advantage of low cost, but is also small enough that a chemical reaction carried out in the device can easily fit directly into the sample compartment of an FTIR spectrometer. Since the device is small an economical quantity of chemical reactants, milligrams instead of grams, can be utilized. The chemicals' cost and disposal problem is greatly reduced, being of great use to the hundreds of industrial and pharmaceutical and university chemists who carry out thousands of such reactions per year.